Film is commonly digitized and transferred either to digital tape or to a computer disk. Once the film is placed in digital form it may undergo additional processing such as color correction, standards conversions, nonlinear editing, “panning and scanning,” compression, and/or various forms of digital filtering.
In the process of correcting the color, the distribution of colors in the film representation are balanced against the visual appearance that the colors have when displayed on a display device. Some of the desired attributes take into account perceptual properties of the human visual system. Certain relationships among color components must be preserved so that, for example, “blacks appear black,” “whites appear white” and color tinted flesh tones appear natural. The corresponding relationships between color distributions and display devices are well-known to experts. For example, it is known how red, green and blue should be mixed in order to look “black” on a given monitor, or to have the appearance of flesh.
The transfer from film to digital format is controllable through various settings on a digitization device which affect the intensities and other properties of the color components. The settings control for “lift”, “gamma,” “gain” and other standard parameters, are implemented digitally from what is recorded to what is output. Some digitization devices allow for the control of the exposure time of each color channel, thereby effectively adjusting the three intensities. Although the details may differ from one device to another (corresponding to a different way of imaging the film), the effects of adjusting the parameters can be observed both mathematically by examining the color histogram and visually by watching the video on standard monitors. In all current systems, an operator supervises the transfer, determines the proper settings for the variables, and is ready to make adjustments as may be needed because of changing characteristics of the material. In particular, current systems are not automated.